This project is directed at evaluating the synthesis, metabolism, and distribution of glycoproteins in developing and adult vertebrate retinas. In particular, this study will focus on one of two major classes of glycoproteins (the "N-linked" type) by taking advantage of the selective inhibitory action of the antibiotic, tunicamycin, on the biosynthesis of N-linked glycoproteins. The visual pigment, rhodopsin, is a member of this class of glycoproteins, and is the major protein constituent of rod outer segment (ROS) membranes. A primary objective of this project is to assess the importance of glycosylation in the intracellular transport and insertion of rhodospin into newly-forming discs in the ROS. The uptake and incorporation of labeled sugars and leucine (glycoprotein precrusors) in the presence and absence of tunicamycin will be monitored by biochemical and autoradiographic techniques in three different systems: (1) adult human retinas in vitro; (2) adult frog (Rana pipiens) retinas in vivo and in vitro; (3) embryonic and juvenile toad (Xenopus laevis) retinas in vitro. The effects of tunicamycin on the histogenesis and morphogenesis of the developing Xenopus retina will be examined, with particular emphasis on the elaboration and maintenance of outer segment membranes. In addition, the effects of tunicamycin on the morphology and viability of retinal cells in the adult frog will be assessed in vivo (by intraocular injection), with particular emphasis on the synthesis and maintenance of normal visual cell outer segment membranes. Although considerable effort has been invested over the past 15 years to understand the means by which photoreceptors normally synthesize and renew their outer segments in an orderly and regulated manner, these processes remain enigmatic. It is presumed that defects in the regulation of these processes (at one or more of several potential loci) lead to outer segment deterioration, with ensuing visual cell degeneration and eventual blindness. New information will be derived from proposed research which will significantly advance an understanding of the role of glycoproteins in the development and maintenance of retinal cells, particularly visual cells. Such information will form a basis for further studies directed at the regulatory mechanisms involved in retinal glycoprotein synthesis and utilization in normal and disease states, particularly in regard to the etiology of photoreceptor degenerations.